org.erights.e.elib.base
Class Ejector

java.lang.Object
  |
  +--org.erights.e.elib.base.Ejector

All Implemented Interfaces:

OneArgFunc, Runnable

public class Ejector

extends Object

implements OneArgFunc, Runnable

Untamed: An Ejector implements a non-local exit construct that can return a value. It works with an EscapeExpr to cause an escape to take place. When used directly from java, a typical pattern is:

      Ejector ejector = new Ejector();
      //cause ejector to be appropriately accessible from the try
      //block
      try {
          //blah blah blah
          if (we need to exit) {
              ejector.run(result);
          }
          //blah blah blah
      } catch (Ejection ej) {
          Object result = ejector.result(ej);
      } finally {
          ejector.disable();
      }
 

Author:

Mark S. Miller

Field Summary

private Ejection	myEjection
private boolean	myIsEnabled
private String	myName
private Object	myResult

Constructor Summary

Ejector(String optName)
Enabled:

Method Summary

void	disable() Enabled: To avoid confusion, one should always disable an Ejector in a finally block on the way out of its catching context.
boolean	isEnabled() Enabled:
boolean	isMine(Throwable t) Enabled: Broken out into a separate public test so Ejection catchers can easily test against several Ejectors.
Object	result(Throwable t) Enabled: Having caught a possible Ejection, the catcher asks an Ejector for the result corresponding to that Ejection.
void	run() Enabled: Non-local exit returning null.
Object	run(Object result) Enabled: Non-local exit returning 'result'.
String	toString() Suppressed:

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

myName

private final String myName

myIsEnabled

private boolean myIsEnabled

myResult

private Object myResult

myEjection

private Ejection myEjection

Constructor Detail

Ejector

public Ejector(String optName)

Enabled:

Parameters:

optName -

Method Detail

isEnabled

public boolean isEnabled()

Enabled:

Returns:

disable

public void disable()

Enabled: To avoid confusion, one should always disable an Ejector in a finally block on the way out of its catching context.

isMine

public boolean isMine(Throwable t)

Enabled: Broken out into a separate public test so Ejection catchers can easily test against several Ejectors.

result

public Object result(Throwable t)

Enabled: Having caught a possible Ejection, the catcher asks an Ejector for the result corresponding to that Ejection. If this Ejection was indeed thrown by this Ejector, the corresponding result returned. Otherwise, the Ejection is rethrown.

run

public void run()

Enabled: Non-local exit returning null.

Equivalent to 'run(null)'.

Specified by:

run in interface Runnable

See Also:

java.lang.Thread#run()

run

public Object run(Object result)

Enabled: Non-local exit returning 'result'.

Would normally return void, but to minimize on Deflectors, and since we're not returning anything anyway, we implement OneArgFunc, and so must return Object.

Specified by:

run in interface OneArgFunc

toString

public String toString()

Suppressed:

Overrides:

toString in class Object

Returns:

a string representation of the object.